Method of forming graduations and other markings on a surface-coated metal article

ABSTRACT

1. A METHOD OF MANUFACTURING A SURFACE-COTED METAL ARTICLE HAVING AT ITS SURFACE A DESIRED PATTERN OF VISIBLE GRADUATIONS AND OTHER MARKINGS, COMPRISING THE STEPS OF: (A) PROVIDING A METAL BLANK WITH A PROTECTIVE METAL PLATING OVER THE ENTIRE SURFACE WHICH IS TO BE GRADUATED AND MARKED; (B) APPLYING AN ADHERENT MASKING COMPOUND TO THE PLATING SURFACE SO AS TO LEAVE THAT SURFACE EXPOSED AT SELECTED AREAS IN THE FORM OF THE DESIRED PATTERN OF GRADUATIONS AND OTHER MARKINGS, BUT IN WHICH LINES DEFINING THAT PATTERN ARE NARROWER THAN CORRESPONDING LINES TO BE PRODUCED IN THE DESIRED FINISHED PATTERN; 8C) ELECTROLYTICALLY STRIPPING THE EXPOSED METAL PLATING AT THE SAID PATTERN LINES SO AS TO EXPOSE THE METAL BLANK THEREBENEATH; (D) CHEMICALLY ETCHING THE METAL BLANK EXPOSED AT THE SAID PATTERN LINES SO AS TO PRODUCE A PATTERN OF GRADUATIONS AND MARKINGS IN A COLOUR CONTRASTING WITH THE COLOUR OF THE METAL PLATING; (E) CHEMICALLY ETHCHING AWAY, FROM THE REAR, PARTS OF THE MASKED PLATING WHICH ARE LEFT OVERHANGING THE ETCHED AREAS OF THE BLANK AS A RESULT OF THE PRECEDING ETCHING STEP; AND (F) REMOVING THE MASKING COMPOUND TO REVEAL THE PLATED ARTICLE BEARING THE FINISHED PATTERN OF GRADUATIONS AND OTHER MARKINGS AS DEFINED BY PATTERN LINES OF DESIRED WIDTH.

United States ?atent O 3,846,263 METHOD OF FORMING GRADUATIONS AND OTHER MARKINGS ON A SURFACE-COATED METAL ARTICLE Edmund Day, Woodhouse 9WP, Sheflield, England No Drawing. Continuation-impart of application Ser. No. 200,628, Nov. 19, 1971, which is a continuation of application Ser. No. 831,757, June 9, 1969, both now abandoned. This application Oct. 26, 1973, Ser. No. 410,023 Claims priority, application Great Britain, June 13, 1968, 28,227/ 68 Int. Cl. C23b 3/04 US. Cl. 204-129.65 4 Claims ABSTRACT OF THE DISCLOSURE A surface-coated metal article, for example a metal measuring rule, comprises a steel blank coated all over with a protective layer of satin chrome plating and hearing a pattern of contrasting graduations and other markings formed by electrolytically stripping the plating through an adherent masking compound at areas having the form of the desired pattern of graduations and other markings but in which lines defining the pattern are narrower than the corresponding lines in the desired finished pattern, chemically etching the exposed steel blank, etching from the rear parts of the masked plating which are left overhanging the etched areas by the preceding step, and finally removing the masking compound to reveal the desired pattern defined by lines of the desired width.

This application is a continuation-in-part of the application Ser. No. 200,628 in the name of Edmund Day, filed Nov. 19, 1971, and now abandoned, which Was itself a streamlined continuation application based on application Ser. No. 831,757 in the name of Edmund Day, filed June 9, 1969 and now abandoned.

This invention relates to a method of manufacturing surface-coated metal articles having on their surfaces a pattern of visible graduations or other markings, and to articles made by such a method. Such an article may comprise for example a metal measuring rule.

For such a rule the surface coating may comprise a protective coating for the underlying metal body of the rule whereby to protect it from corrosion, for example, by rusting in the case of a steel rule. Preferably, the protective coating should not be highly reflective, so as to avoid glare when in use, and it is of prime importance that the rule should be permanently and accurately marked in an easily visible way.

In the past some rules have been manufactured by marking a blank (normally by etching), by subsequently plating it completely with a satin chrome layer (to provide a glare-free surface), and finally by filling the marked areas with a black enamel to provide good contrasting markings.

This process is not entirely satisfactory since filling the markings is a time consuming and awkward step unsuited to modern production techniques. Moreover, with use, and especially for flexible metal rules, the enamel filling tends to become dislodged.

Whilst as an alternative it is possible to plate the blank completely with a layer of satin chrome, and then after masking the rule except where markings are required to chemically etch through the unmasked parts of the chrome layer and into the underlying surface of the steel in a single operation using a suitable mordant, the depth of etch so produced will be uneven due to the variation that occurs in the thickness of the chrome layer, the latter normally being thicker at the edges of the rule. Thus the underlying steel surface may not be etched at all in some places that are to be marked, and hence the markings so produced will not be satisfactory.

STATEMENT OF INVENTION According to the present invention a method of manufacturing a surface-coated metal article having at its surface a desired pattern of visible graduations and other markings, comprises the steps of:

(a) providing a metal blank with a protective metal plating over the entire surface which is to be graduated and marked;

(b) applying an adherent masking compound to the plating surface so as to leave that surface exposed at selected areas in the form of the desired pattern of graduations and other markings, but in which lines defining that pattern are narrower than corresponding lines to be produced in the desired finished pattern;

(c) electrolytically stripping the exposed metal plating at the said pattern lines so as to expose the metal blank there-beneath;

(d) chemically etching the metal blank exposed at the said pattern lines so as to produce a pattern of graduations and markings in a colour contrasting with the colour of the metal plating;

(e) chemically etching away, from the rear, parts of the masked plating which are left overhanging the etched areas of the blank as a result of the preceding etching step; and

(f) removing the masking compound to reveal the plated article bearing the finished pattern of graduations and other markings as defined by pattern lines of desired width.

A method of manufacturing a surface-coated metal article having at its surface a desired pattern of visible graduations and other markings, may comprise the steps of:

(a) providing a steel blank with a protective satin chrome plating over the entire surface which is to be graduated and marked;

(b) applying an adherent masking compound to the plating surface so as to leave that surface exposed at selected areas in the form of the desired pattern of graduations and other markings, but in which lines defining that pattern are narrower than corresponding lines to be produced in the desired finished pattern;

(c) electrolytically stripping the exposed chrome plating at the said pattern lines so as to expose the steel blank therebeneath;

(d) chemically etching the steel blank exposed at the said pattern lines so as to produce a pattern of graduations and markings in a colour contrasting with the colour of the chrome plating;

(e) chemically etching away, from the rear, parts of the (f) removing the masking compound to reveal the plated article bearing the finished pattern of graduations and other markings as defined by pattern lines of desired width.

The above methods may be applied to the manufacture of a surface-coated metal measuring rule.

The invention will now be described in greater detail with reference to a preferred method of manufacturing a chrome faced metal rule having a glare free surface. The process will be described as applied to an already prepared blank of tempered steel.

The blank is initially given a matt surface by vapour blasting, although any other suitable method, such as sand blasting or shot blasting, may be used. Chemical methods might also be contemplated. The matted blank is then given a satin chrome facing on either side by hard chrome plating directly onto the steel.

The plated blank is then masked prior to the marking operations to be described. The masking of the regions not to be marked may be carried out by a normal photoresist method. This may be done by dipping the blank into a photo-resist solution, such as polyvinyl alcohol and potassium bichromate, exposing the dried coating to the ultra-violet light masked by a negative stencil so that the coating hardens in the region which was exposed to the light, and removing the remaining portion of the coating, this portion defining the marks to be made on the rule, by washing the blank in warm water or a developer as is suitable for the particular photo-resist solution employed.

The blank thus masked is then subjected to three different processes. The first comprises the electrolytic stripping of the exposed chrome so as to expose the surface of the steel. This is suitably done in a cold bath of sodium hydroxide solution (say, 12 oz. of sodium hydroxide per gallon of water) with the steel rule as the anode. When the steel surface is exposed to define the markings the rule is removed, whereupon the second process, a chemical etching process, is effected in a solution which will etch the steel surface is exposed to define the markings the rule does not attack the chrome. Unfortunately, the steel surface is etched not only inwardly, but also sideways under the chrome layer so that when the rule is removed from the etching solution there is an overhang of chrome. This is then chemically etched away by a third process in a solution comprising 5 parts of nitric acid, 20 parts of hydrochloric acid and 30 parts of water. The photo-resist mask is then removed and the rule is finished by grinding its edges and ends.

A rule thus manufactured has its markings etched into the surface of the steel, and these are clearly visible in black as a result of the chemical action with the steel. This visible marking does not tend to flake away as in the known rules already described.

Furthermore, the depth of etch in the underlying steel will be fairly uniform, since the time of immersion in the electrolytic bath can be safely extended so as to remove even the thickest areas of chrome without over-etching areas which carry a thinner layer of chrome.

The thickness of the chrome layer and the depth and width of the markings are similar to those in known rules, the dimensions of the markings being dependent upon the separation between the graduations of the rule in question. It will be appreciated that the above referred to masking will expose areas considerably narrower than those actually obtained due to the sideways effect of the etching and the final removal of the chrome overhang. Thus a masked line of 0.002 ins. becomes, say, a 0.004 in. line after etching.

The manner of masking the blank is not restricted to that described.

What is claimed is:

1. A method of manufacturing a surface-coated metal article having at its surface a desired pattern of visible graduations and other markings, comprising the steps of:

(a) providing a metal blank with a protective metal plating over the entire surface which is to be graduated and marked;

(b) applying an adherent masking compound to the plating surface so as to leave that surface exposed at selected areas in the form of the desired pattern of graduations and other markings, but in which lines defining that pattern are narrower than corresponding lines to be produced in the desired finished pattern;

(c) electrolytically stripping the exposed metal plating at the said pattern lines so as to expose the metal blank therebeneath;

(d) chemically etching the metal blank exposed at the said pattern lines so as to produce a pattern of graduations and markings in a colour contrasting with the colour of the metal plating;

(e) chemically etching away, from the rear, parts of the masked plating which are left overhanging the etched areas of the blank as a result of the preceding etching step; and

(f) removing the masking compound to reveal the plated article bearing the finished pattern of gradnations and other markings as defined by pattern lines of desired width.

2. A method of manufacturing a surface-coated metal article having at its surface a desired pattern of visible graduations and other markings, comprising the steps of:

(a) providing a steel blank with a protective satin chrome plating over the entire surface which is to be graduated and marked;

(b) applying an adherent masking compound to the plating surface so as to leave that surface exposed at selected areas in the form of the desired pattern of graduations and other markings, but in which lines defining that pattern are narrower than corresponding lines to be produced in the desired finished pattern;

(c) electrolytically stripping the exposed chrome plating at the said pattern lines so as to expose the steel blank therebeneath;

(d) chemically etching the steel blank exposed at the said pattern lines so as to produce a pattern of graduations and markings in a colour contrasting with the colour of the chrome plating;

(e) chemically etching away, from the rear, parts of the masked plating which are left overhanging the etched areas of the blank as a result of the preceding etching step; and

(f) removing the masking compound to reveal the plated article bearing the finished pattern of graduations and other markings as defined by pattern lines of desired width.

3. A method of manufacturing a surface-coated metal measuring rule having at its surface a desired pattern of visible graduations and other markings, comprising the steps of:

(a) providing a steel blank with a protective satin chrome plating over the entire surface which is to he graduated and marked;

(b) applying an adherent masking compound to the plating surface so as to leave that surface exposed at selected areas in the form of the desired pattern of graduations and other markings, but in which lines defining that pattern are narrower than corresponding lines to be produced in the desired finished pattern; v

(c) electrolytically stripping the exposed chrome plating at the said pattern lines so as to expose the steel blank therebeneath;

(d) chemically etching the steel blank exposed at'the said pattern lines so as to produce a pattern of graduations and markings in a colour contrasting with the colour of the chrome plating;

(e) chemically etching away, from the rear, parts of 3,846,263 5 6 the masked plating which are left overhanging the References Cited iiiii l tefilfi as a result of the UNITED STATES PATENTS (f) removin the masking compound to reveal the 2,171,504 8/1939 Keuffel et 33137 R plated article bearing the finished pattern of gradu- 5 ations and other markings as defined by pattern lines JOHN MACK Primary Exammer of desired width. W. I. SOLOMON, Assistant Examiner 4. A surface-coated metal measuring rule bearing a pat- U S Cl X R tern of graduations and other markings produced by a process according to Claim 3. 10 33-137 R; 1178.5; 1563, 8; 204-35 R 

1. A METHOD OF MANUFACTURING A SURFACE-COTED METAL ARTICLE HAVING AT ITS SURFACE A DESIRED PATTERN OF VISIBLE GRADUATIONS AND OTHER MARKINGS, COMPRISING THE STEPS OF: (A) PROVIDING A METAL BLANK WITH A PROTECTIVE METAL PLATING OVER THE ENTIRE SURFACE WHICH IS TO BE GRADUATED AND MARKED; (B) APPLYING AN ADHERENT MASKING COMPOUND TO THE PLATING SURFACE SO AS TO LEAVE THAT SURFACE EXPOSED AT SELECTED AREAS IN THE FORM OF THE DESIRED PATTERN OF GRADUATIONS AND OTHER MARKINGS, BUT IN WHICH LINES DEFINING THAT PATTERN ARE NARROWER THAN CORRESPONDING LINES TO BE PRODUCED IN THE DESIRED FINISHED PATTERN; 8C) ELECTROLYTICALLY STRIPPING THE EXPOSED METAL PLATING AT THE SAID PATTERN LINES SO AS TO EXPOSE THE METAL BLANK THEREBENEATH; (D) CHEMICALLY ETCHING THE METAL BLANK EXPOSED AT THE SAID PATTERN LINES SO AS TO PRODUCE A PATTERN OF GRADUATIONS AND MARKINGS IN A COLOUR CONTRASTING WITH THE COLOUR OF THE METAL PLATING; (E) CHEMICALLY ETHCHING AWAY, FROM THE REAR, PARTS OF THE MASKED PLATING WHICH ARE LEFT OVERHANGING THE ETCHED AREAS OF THE BLANK AS A RESULT OF THE PRECEDING ETCHING STEP; AND (F) REMOVING THE MASKING COMPOUND TO REVEAL THE PLATED ARTICLE BEARING THE FINISHED PATTERN OF GRADUATIONS AND OTHER MARKINGS AS DEFINED BY PATTERN LINES OF DESIRED WIDTH. 